Food packaging fulfills many essential functions. It protects food from detrimental physical, chemical, and biological influences. The containment function enables distribution and prevents product losses through spillage, friction of loose materials, and mixing of different products. Packaging adds convenience to food and facilitates accessibility and easy preparation. As a communication medium, it informs the consumer about a product’s content, shelf life, and storage conditions [1
]. Food packaging also contributes to sustainability, since it prevents food waste and allows for an efficient distribution of the products [2
]. Notwithstanding the aforementioned benefits, food packaging is increasingly required to become more sustainable, since the production, use, and disposal of a packaging are associated with a multitude of environmental impacts [4
], hence referred to as direct effects.
In addition to the direct effects, there are also adverse environmental effects indirectly caused by inadequate packaging, such as packaging-related food losses and waste (FLW). Per definition, food losses occur during production and processing, while food waste refers to the losses at the end of the supply chain, namely during retail and end-consumption [6
]. The reasons for FLW are manifold and to a certain extent related to packaging [7
]. For example, food degrades if the packaging does not provide proper protection against oxygen, moisture, and microbes. Packaging failures can cause damage during transportation. Packaging that is not easy to empty or portion sizes which are too large may lead to FLW at the end-consumer stage [2
]. Recent research shows that the environmental burden of FLW often exceeds that of packaging [8
Moreover, food leftovers can negatively affect the recyclability of packaging [12
]. Recyclability is an important property of circular packaging. The concept of circularity in the context of sustainable production describes the restorative and preservative character of a product. In contrast to a linear product, a circular product contains renewable or recycled content or reused parts and is compostable, recyclable, or reusable, and was produced using renewable energy [14
As part of its effort to transform Europe’s economy into a more sustainable one, the European Union adopted a new set of measures, commonly referred to as the Circular Economy Package. These measures include several legislative proposals on waste, which aim to increase recycling rates, boosting the uptake of secondary material by industry, reducing food waste and promoting nontoxic life cycles [16
]. The amended Directive on Packaging and Packaging Waste [17
] will have far-reaching consequences for the packaging supply chain, because higher recycling rates require a redesign of packaging and massive investment in recycling infrastructure. The European Council approved the amendments in 2018 [18
]. Moreover, leading brands, retailers, and packaging companies committed themselves to the goals of the circular economy and working towards 100% reusable, recyclable, or compostable packaging by 2025 or earlier [19
The waste hierarchy, as defined in article 4 of Directive 2008/98/EC on waste, ranks the different end-of-life alternatives and clearly explicates which options (a. prevention, b. preparing for reuse, c. recycling, d. other recovery, and e. disposal) are preferable from an environmental point of view [20
]. Although the waste hierarchy is in most cases supported by life cycle assessment (LCA) [21
], there are notable exceptions [23
]. Replacing nonrecyclable, lightweight flexible packaging with alternative, easy-to-recycle packaging materials may lead to adverse environmental effects [24
]. It is, however, important to note that circularity is rather a political and legal requirement for packaging producers and not per se environmentally preferable.
Taken together, the abovementioned findings suggest that it is necessary to take the following environmental aspects into account, when assessing the environmental sustainability of packaging.
Direct environmental impacts caused by the production and disposal of packaging.
Indirect environmental impacts caused by, e.g., packaging-related FLW.
Circularity of packaging.
The basis for improvement in these fields is measuring direct and indirect effects in addition to the circularity of packaging in a comprehensible way. Hence, quantification of the environmental performance of packaging is a prerequisite for management of the environmental impacts of packaging.
Against this background, the present study on the one hand aims to identify the most relevant Key Environmental Performance Indicators (KEPIs) for food packaging. These KEPIs should cover the most relevant aspects of environmental sustainability, without disguising potential conflicts of interests and tradeoffs between different aspects. Moreover, they should support decision-making at the product level. Equally important is the question, which methods are best suitable for calculating these KEPIs. On the other hand, the study aims to set up a methodological framework for a holistic environmental assessment of food packaging. The focus of this work is on the environmental aspects of packaging hence the aspect of human health is not considered.
The point of departure for this paper is the underlying hypothesis that existing frameworks and methodologies need further refinement, because either they ignore important aspects or they are so unspecific, that they do not give guidance on how to calculate the relevant indicators in a scientifically substantiated and comparable manner.
3. Proposed Methodological Framework
The proposed framework defines minimum requirements for an extended life cycle assessment of packaging. It follows the consecutively explained guiding principles. This section outlines the guiding principles, defines requirements for LCA calculation and describes how the aspects of food waste and circularity can be included in the analysis. After introducing the guiding principles of the proposed framework, lists with recommended indicators with corresponding calculation procedures are given.
3.1. Guiding Principles for Methodological Choices
The assessment of packaging should always take into account the direct and indirect effects of packaging and should comprise additional information about the circularity of a packaging. Figure 3
illustrates the concept.
The following proposed framework shall be set up of methods that are practicable and comprehensible. Practicability means that calculations can be conducted using standard LCA tools and datasets. In contrast to the abovementioned methodological frameworks, the here-proposed framework does not only describe general principles, it also explains how the relevant indicators should be calculated by referring to literature.
An important goal of this work is to streamline calculation procedures and assessed indicators to facilitate comparability. Therefore, practitioners should follow the latest PEF recommendations as far as possible. It aims to support business with complying with existing and forthcoming European regulation and standardization efforts. It explicitly refers to the Circular Economy Package of the EU and the PEF initiative.
Although many indicators can be calculated, the number of indicators should be reduced to a clearly arranged number of KEPIs suitable for decision-making processes, including product comparison and single-product optimization. Guidance on indicator selection processes is given in the following subsections.
3.2. Basic Information Concerning the Packaging
Alongside the results of the KEPIs, some basic information concerning the packaging and the validity of the calculated values must be reported:
the weight, construction, and material composition of the packaging
the functional unit of the studied system (quantified performance of packaging)
the spatial and temporal validity of the calculated values
The results of life cycle impact assessment and recyclability assessment are only valid for a defined geographical region and refer to a specific time span [41
3.3. Recommendations for the Calculation of the Environmental Impacts Directly Caused by Packaging
The procedures for calculating environmental impacts of packaging are oriented towards the latest recommendations published in the context of the environmental footprint pilot phase (European Commission, 2018). These recommendations might be subject to minor changes during the coming years. No standalone PEFCR exists for packaging, thus the recommendations given here are solely oriented to the PEF recommendations.
The full life cycle of the packaging should be modeled, considering the following life cycle stages.
For the calculation, primary data and PEF-compliant datasets for secondary data should be used. End-of-life of packaging has to be modeled using the Circular Footprint Formula. If no primary data are available for parameters such as recycling output rate or quality ratio, default values provided by the European Commission can be used. In this case, a sensitivity analysis should be performed to check how different end-of-life assumptions influence the total result.
The 16 recommended impact categories should be assessed and subsequently reduced to the three most relevant categories using the recommended normalization and weighting factors [88
]. These three most relevant impact categories are used for decision-making and communication purposes. They are the basis for identifying the most relevant processes of a packaging’s life cycle, which are those that contribute more than 80% to any of the most relevant impact categories identified. Table 3
presents a list of these 16 impact categories and the corresponding life cycle impact assessment methods.
3.4. Recommended Indicators for Packaging-Related FLW
The environmental impacts of the packaged food should be calculated. Based on the greenhouse gas emissions, the FTP ratio [78
] should be calculated by dividing the environmental impacts of food (Efood
) by the environmental impacts of packaging (Epackaging
The FLW rate is calculated by dividing the amount packaging-related FLW by the total amount of packaged food. Greenhouse gas emissions of packaging-related FLW have to be calculated.
Packaging properties do not directly influence FLW rates. Therefore, the amount of packaging-related FLW has to be collected empirically. To date it is not possible to determine exactly the rate of packaging-related FLW. We recommend a scenario-based approach to characterize the possible environmental impacts of packaging-related FLW in the case of lacking data. The amount of food wasted due to the inability to empty the packaging entirely can be determined by emptying a sample of packaging in a structured manner and weighing the residues. Literature data about the amount of packaged food wasted at retail and consumer level is available [79
]. The PEFCR guidance document provides a list with default product loss rates [75
]. Although scenarios can be derived from this data, they have to be interpreted with great care, since total loss rates generally exceed the packaging-related FLW rates.
Additional qualitative information regarding packaging features that help to reduce FLW needs to be provided if relevant. These qualitative considerations refer to resealability, appropriateness of packaging size and protective properties of packaging. Table 4
presents a list of recommended indicators.
3.5. Recommended Circularity Indicators
The circularity indicators as listed below (Table 5
) should be assessed if relevant for the studied packaging.
We recommend the use of qualitative recyclability assessment [90
] in the form of an expert judgment, supplemented by semiquantitative [94
] or purely quantitative approaches [12
]. However, an evaluation of the recyclability has to consider country-specific characteristics of existing waste management systems and recycling infrastructure.
3.6. Recommendations for the Interpretation of Results
Practitioners must clearly delineate the potential conflicts of interest revealed by the analysis. They should be well aware of the fact that—from an environmental point of view—reducing environmental impacts of the integrated food-packaging system is clearly preferable to improving the circularity of a product. Although packaging manufacturers are increasingly confronted with the demand for more recyclable packaging, they must always keep in mind that recyclability should not compromise the protective function of the packaging. The same is true for the use of renewable materials: they are more circular than fossil-based materials; however, they can lead to adverse environmental effects such as increased eutrophication [95
An important part of the interpretation is the analysis of the most relevant processes, which indicate the most effective levers for improvement. A sensitivity analysis demonstrates to which extent the results are influenced by assumptions.
Packaging is under intense public scrutiny and regarded as a source of waste and pollution. Therefore, packaging producers are increasingly required to make packaging more sustainable. Most guidelines on packaging sustainability agree on a general definition of sustainable packaging. It has to provide optimal product protection, be safe for human health and cyclic while having the smallest possible ecological footprint.
Countless LCAs on food packaging have been conducted; however, few consider the interaction between the packaging and packaged food, although it is widely acknowledged that this interaction plays a key role for the environmental performance of food packaging.
The most important finding of this paper is that although many guidelines on packaging sustainability exist, detailed guidance on how to calculate KEPIs for packaging is surprisingly scarce which is why a measurement tool for packaging sustainability is required.
4.1. Demand for Standardization
The current proliferation of differing methods to assess the environmental performance of products leads to mistrust in environmental performance information and may increase cost for business [68
]. Mandatory footprint information on products would influence consumer behavior and support sustainable purchasing decisions [96
]. Such an approach would require a high degree of standardization of calculation procedures to allow for a fair comparison. As a result of this, the EU member states and industry requested the European Commission to develop a standardized European method for the calculation of the environmental footprint of products and organizations [97
]. We support the goals of the PEF initiative and therefore the proposed measurement tool is oriented towards the PEF methodology. We acknowledge that there are challenges and that the criticism [72
] is partly justified; in particular, the criticism regarding the as yet unclear policy outcome of the PEF process. Without clearly communicating the reason of developing another standard, there is a risk that the PEF initiative may even add to confusion and proliferation. Another problematic issue is cross-study comparability of results. A fair comparison between two products is only possible if the studies were conducted using exactly the same methodology, applying identical high quality standards regarding primary data and where full functional equivalency of the two products is given. Even if these two products are calculated using the same PEFCR and the same data basis for secondary data, it is—in practice—unlikely that all before mentioned requirements are met. This is a challenge of LCA studies in general and not specifically related to PEF, however, the PEF initiative may possibly lead consumers to compare products, which are not comparable. For good reasons, ISO 14044 requires high standards for comparative assessments. A harmonized approach can gradually improve comparability, but not provide full and fair cross-study comparability. Reproducibility and cost reduction will be achieved by reducing the number of methodological choices.
Some problematic issues of the original PEF proposal [68
], for example the end-of-life allocation formula and inappropriate assessment methods for water and land use, have been addressed by the Joint Research Center, and significant improvements could be achieved [75
]. The criticism directed to the PEF approach towards prioritization of impact categories using normalization and weighting [99
] may be justified from a purely scientific point of view; however, in practice, prioritization of impact categories is carried out implicitly [97
]. For example, a Product Carbon Footprint study attaches more importance to climate change than to other impact categories, although this may not always be justified. Steinmann et al. [63
] elaborated an approach towards indicator selection based on an analysis of the correlation of impact category results and proposed a set of three indicators including land use, climate change, and human toxicity, because these indicators are the least correlated and cover a wide range of potential environmental implications. This science-based method avoids subjectivity, although it does not address the fact that environmental problems are not equally important [100
Taken together, these arguments underline the importance of developing a harmonized European LCA approach, although there are still unresolved issues. Standardization would not only improve comparability and reproducibility of LCA calculations, it would be equally beneficial for the assessment of packaging-related FLW and circularity.
4.2. Reasons for Including Packaging-Related FLW
A growing body of literature has addressed the environmental relevance of packaging-related FLW. It has been shown, in some cases, that the environmental impacts of the production and disposal of wasted food by far exceeds the environmental impact of packaging [9
]. In most cases, it is challenging or even impossible to determine the rate of packaging-related food losses and waste [7
]. Therefore, even though data is restricted or non-existent, this paper aims to provide a systematic approach to include packaging-related FLW. A calculation of the food to packaging ratio can be conducted and a description of certain packaging features such as emptiability, resealability, and appropriateness of packaging size can be given nonetheless. A mandatory inclusion of this issue in packaging LCA can help to draw the role of packaging for food waste reduction strategies to the attention of packaging designers and retailers.
4.3. Reasons for Including Circularity
The main reason for including the abovementioned circularity indicators in sustainability assessment is that they are highly relevant for the environmental performance of packaging. They represent some of the most important levers to improve packaging sustainability, because packaging producers can directly influence parameters such as recyclability or share of used renewable energy. Moreover, it became a legal requirement to make packaging more circular. Nonetheless, the transition towards a circular economy is not a goal in itself; it should deliver ecological goals [101
]. Packaging designers should always apply life cycle thinking to verify that, e.g., improved recyclability in fact contributes to the overarching goal of reduced environmental impacts.
The circularity metrics proposed in this paper focus on cyclic material and renewable energy flows. While most of the indicators can be assessed relatively easy, this is not the case for the recyclability assessment. A recyclability assessment requires a good understanding of the available recycling infrastructure and the suitability of a packaging to be reprocessed into a useful secondary material. For the determination of the downcycling factor, which is required for the calculation of the environmental burdens and benefits of recycling, it is necessary to understand the market situation of recyclables [70
While many LCAs confirm the environmental benefits of reuse and recycling, the case is not so clear with biobased and compostable materials. The mechanical and barrier properties of biobased polymers have been significantly improved during the last years, which makes them increasingly suitable for food packaging [27
]. Although biobased products decrease the dependency from fossil fuels, this may come at the price of more land use and other adverse environmental effects of agriculture [102
]. Industry could overcome this drawback by using biowaste as a source for bioplastic precursors [103
]. The European Union encourages the substitution of fossil raw materials with biobased materials as part of the bioeconomy strategy [104
]. Compostability of packaging is often promoted as “environmental friendly” and a possible solution to the crisis of marine littering. According to the Waste directive 2008/98/EC, composting or reprocessing of organic material is a form of recycling. Compostable packaging generally only degrades in an industrial composting plant [105
] and not in nature, therefore it is not a solution to the littering problem. It is problematic to define the composting of packaging as recycling because biopolymers do not contain plant nutrients and, therefore, their degradation does not lead to the formation of valuable manure. Rossi et al. [106
] showed that mechanical recycling of polylactic acid would be preferable to composting. Moreover, compostable bags may cause problems in industrial composting plants, because they have to be manually removed owing to the fact that they are not easily distinguishable from conventional plastic bags [107
The use of the material circularity indicator [86
] is only optional because packaging designers should rather focus on identifying and improving the most relevant circularity metric. The material circularity indicator does not account for biological cycles, differing market situations for recyclables or the use of renewable energy. It credits product longevity, which is usually not relevant for food packaging.
4.4. Future Research and Data Requirements
The concept of packaging-related FLW needs further refinement. Future research should focus on the development of standardized procedures to quantify packaging-related FLW. Further work is required to collect data about packaging-related food losses and waste for different food categories and packaging types.
Further studies are needed to estimate how improvement of the proposed circularity indicators really reduces the environmental impact over the life cycle of packaging. This could be done by systematically analyzing different packaging. In doing so, circularity metrics can be adjusted to different values and by carrying out sensitivity analyses, the influence of metrics as recycled content, reuse rate, share of renewable energy on the results for the assessed impact categories can be estimated. This procedure could help to reveal the greatest levers for environmental improvement and potential conflict of interests. More data is needed for realistic estimations of recycling output rates for specific packaging types. The development of an open-source measurement tool for packaging recyclability would be highly beneficial for packaging designers and other interested parties along the packaging supply chain, including retailers and recyclers. This measurement tool should ideally cover all types of packaging materials, be adjustable to country-specific differences in waste management systems and allow for a quantitative assessment of packaging recyclability.
This paper has investigated how the environmental sustainability of food packaging can be defined and measured by appropriate indicators. The present research emphasizes the importance of developing a standardized measurement tool, which is in line with European environmental policy. The proposed KEPIs cover three different aspects of packaging sustainability: environmental impacts directly caused by packaging, environmental impacts caused by packaging-related food losses and waste, and circularity. This research has brought to light many questions which require further investigation, especially the unsolved question of how to quantify packaging-related FLW. Nevertheless, we believe our work provides a basis for further methodological developments.